Question

I have a LINQ in a method that is being passed an array of HalfHour objects, each of which contains a DateAndTime and a HalfHourNumber.

I need to query for each of these separately, and then average the result. Currently my query only works for the first element (I’m selecting element [1]):

internal static decimal? Average(this IQueryable<LOSSES> query, HalfHour[] array)
{
     var list = query.ToList();

     var numbers = (from q in list
                    where  q.DAY == array[1].DateAndTime.Date
                    select q).Select(x => Calculations.SingleElement(x, 
                    array[1].HalfHourNumber));

     return numbers.Average();

}

How would I prevent needing to do this within a loop (calling the query multiple times) yet keep the objects properties associated correctly?

Answer 1

To get a list of averages to go with your list of LOSSES:

var averages = list.Select(
    q => array.Where(hh => q.DAY == hh.DateAndTime.Date)
              .Select(hh => Calculations.SingleElement(q, hh.HalfHourNumber)
              .Average()).ToList();

Or, to associate each LOSSES with the average in a dictionary (if LOSSES supports being used as a key):

var averages = list.ToDictionary(
    q => q,
    q => array.Where(hh => q.DAY == hh.DateAndTime.Date)
              .Select(hh => Calculations.SingleElement(q, hh.HalfHourNumber)
              .Average()
);